In general, a fuel cell system includes a fuel cell stack that generates electric energy, a fuel supplier that supplies hydrogen, which is fuel, to the fuel cell stack, an air supplier that supplies air necessary for an electrochemical reaction to the fuel cell stack, a heat and water manager that removes reaction heat of the fuel cell stack to the exterior of the system, adjusts a driving temperature of the fuel cell stack, and executes a water managing function, and a controller that operates the fuel cell system. In particular, the fuel supplier includes a hydrogen tank, a high pressure/low pressure regulator, a hydrogen re-circulator, and the like, the air supplier includes an air blower, a humidifier, and the like, and the heat and water manager includes a coolant pump, a radiator, and the like.
Further, high pressure hydrogen supplied from the hydrogen tank of the fuel supplier is supplied to the fuel cell stack at low pressure through the high pressure and low pressure regulator, and the hydrogen re-circulator has a recirculation blower installed in a recirculation line to re-circulate non-reacted hydrogen left after the hydrogen is used in an anode of the stack into the anode, thereby prompting a reuse of the hydrogen. In the air supplier, dry air supplied by the air blower is humidified by performing a moisture exchange with exhaust gas (e.g., wet air) exhausted from an outlet of a cathode of the stack while passing through the humidifier and is then supplied to an inlet of the cathode of the fuel cell stack.
The stack of the fuel cell system includes an electricity generation assembly in which a plurality of unit cells are continuously arranged, and each of the unit cells is provided as a fuel cell of a unit configured to generate electric energy by the electrochemical reaction of hydrogen and air. The unit cells include a membrane-electrode assembly, and separators disposed adjacent to both sides of the membrane-electrode assembly. In particular, the separators are formed in a plate form having conductivity and each have channels formed to allow fuel and air to flow into a contact surface of the membrane-electrode assembly. In addition, the membrane-electrode assembly has the anode formed on one surface thereof, the cathode formed on the other surface thereof, and an electrolyte membrane formed between the anode and the cathode.
The anode performs an oxidation reaction for the fuel supplied through the channel of the separator to divide the fuel into electrons and hydrogen ions, and the electrolyte membrane moves the hydrogen ion to the cathode. In addition, the cathode performs a reduction reaction for electrons and hydrogen ions supplied from the anode, and oxygen in the air provided through the channel of the separator to generate water and heat.
A portion of the water generated in the cathode by a chemical reaction penetrates the electrolyte membrane and is moved to the anode. When the water moved to the anode remains in a catalyst layer, a reacting amount of catalyst is reduced. Additionally, when the water moved to the anode remains in the channel, a supply path of the hydrogen is blocked. Thus, the anode of the stack is further connected to a water trap that collects and discharges the water remaining in the catalyst layer or the channel, and a purge line that discharges impurities (e.g., including non-reacted hydrogen gas) in the anode to the humidifier.
The water trap is connected a drainage line that discharges the water to the humidifier, and the drainage line includes a drain valve opened every a purge period to discharge the water. In addition, the purge line includes a purge valve to discharge the impurities in the anode every the purge period. However, an apparatus for controlling a purge valve of a fuel cell vehicle according to the related art opens purge valve at a fixed open time, without considering hydrogen concentration in the channel of the anode of the fuel cell stack and the parking time while restarting the vehicle after the vehicle is parked. In other words, since the apparatus for controlling a purge valve of a fuel cell vehicle according to the related art unconditionally opens the purge valve during a fixed time while restarting the vehicle, a consumption amount of hydrogen increases, thereby decreasing fuel efficiency.